The wireless communications network has grown exponentially over the years. A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems, also known as the 4G system, also provide seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS). The 3rd generation partner project (3GPP) network normally includes a hybrid of 2G/3G/4G systems. With the optimization of the network design, many improvements have developed over the evolution of various standards.
The main function of the Session Management (SM) for 2G/3G systems or Evolved Packet System (EPS) SM (ESM) for 4G systems is to support Packet Data Protocol (PDP) context or EPS bearer handling of the user terminal. SM procedures include PDP context activation procedure, secondary PDP context activation procedure, PDP context modification or deactivation procedure, and MBMS corresponding procedures. ESM procedures include PDN connectivity or disconnect procedures and Bearer resource allocation or modification procedures. To establish an EPS bearer in the 4G system, a UE sends a PDN connectivity request to the network. Upon reception of the SM/ESM request message, the network may reject the request with a cause code. For example, one of the cause code is #65—Maximum number of EPS Bearers Reached—indicating that a UE has already reached the maximum number of EPS bearers.
There are a few issues associated with the maximum number of EPS bearers. First, after the maximum number of active EPSB is reached, the UE may get another request from the network for activating a new EPSB. The UE behavior is not defined under such scenario. Second, the maximum number of bearers is RAT Radio Access Technology (RAT) dependent. If the number of active bearer exceeds the maximum number when system/RAT changes, the UE behavior is also not defined under such scenario. The undefined UE behavior will result in problems when the maximum bearer number is un-synced between the UE side and the network side. If the maximum bearer number at the UE side is higher than the network side, then the network will receive unexpected air message and cause resource wasted. On the other hand, if the maximum bearer number at the UE side is lower than the network side, then the UE will over-restrict and not send out PDN connectivity request, which cause degraded user experience.
A solution is sought for maintaining a precise maximum number of bearers when the maximum number of EPS bearers has reached.